1. Field of the Invention
The present invention relates to a cathode material.
2. Description of the Related Art
It is desired that secondary batteries for electric vehicles have a high energy density to increase driving distance and also have excellent output characteristics when the current density instantaneously changes during high speed running or hill-climbing (hereinbelow, sometimes referred to as an instantaneous output characteristics).
Heretofore, nickel-hydrogen secondary batteries comprising two active materials different in charge and discharge characteristics, that is, a high-output type cathode active material and a low-output type cathode active material have been known as secondary batteries having high energy density and excellent instantaneous output characteristics. The nickel-hydrogen secondary batteries have nickel hydroxide as a cathode active material, and comprise a high-output type cathode active material and a low-output type cathode active material that have different masses of the nickel hydroxide (for example, refer to WO2003/026054).
However, conventional technique mentioned above is an invention related to nickel-hydride secondary battery, and the above-mentioned patent document does not disclose or suggest a lithium ion secondary battery.